The present invention relates to a dialysate supply unit and a blood dialyzing apparatus including the dialysate supply unit, and more particularly, to a dialysate supply unit, which is configured to improve water exchange and mass transfer between blood and dialysate by quickly changing the dialysate pressure in a hemodialyzer using a pulsatile dialysate flow.
When there is a kidney dysfunction, water and waste products that have to be discharged out of body accumulate in blood and imbalance of electrolytes in the body occurs. Most commonly performed to improve such a kidney failure symptom, is hemodialysis which is to circulate blood out of body and rid the blood of the accumulated uremic toxin and excess water by a semi-permeable dialysis membrane. Hemodialysis is a method of seeking an electrolyte balance and ridding the body fluid of uremic toxin and excess water, taking advantages of diffusion applied due to the concentration difference and filtration applied due to the pressure difference between blood and dialysate. Most commonly used of hemodialyzer is the type that is a cylinder-shape container charged with a bundle of hollow fiber membranes and port-processed at both ends thereof by use of a synthetic resin like polyurethane. It is because the hollow fiber hemodialyzer has excellent mass-transfer efficiency resulting from large effective surface area between blood and dialysate compared to the small size as a whole.
A hemodialysis apparatus includes a hemodialyzer, a blood pump designed to supply a patient's blood to the hemodialyzer, a dialysate supply unit that supplies or discharges dialysate. Blood and dialysate each decrease their hydrostatic pressure while passing through a hemodialyzer. Since blood and dialysate flow in opposite directions inside the hemodialyzer, a filtration occurs at the proximal part of the hemodialyzer such that water in the blood moves toward dialysate compartment because blood pressure is higher than dialysate pressure, while a backfiltration occurs at the distal part such that water in the dialysate moves toward blood domain for the same reason. When a filtration takes place, wastes in blood are also eliminated, which is referred to as a convective mass transfer. It is known that uremic toxins of medium molecular size are efficiently removed by the convective mass transfer and thus dialysis efficiency and prognosis on patients have greatly improved. However, there is a big hurdle in the effort to improve dialysis efficiency by the convective mass transfer, because hemodialyzers in typical hemodialysis apparatuses are limited in size and blood flow rate is restrictively allowed to be increased in consideration of the weight and blood vessel condition of a patient.